The present invention relates to combustion gas seals for injectors.
As an example, Japanese Laid-Open Patent Publication No. 2002-364494 describes a conventional installation procedure for a combustion gas seal for injectors. More specifically, the publication discloses an installation procedure for a resin combustion gas seal for an injector and a correction jig used for the gas seal. The gas seal is installed in an annular installation groove defined in a nozzle portion of the injector for sealing an annular space defined between the injector and a recess in which the injector is installed. When fitted into the installation groove, the gas seal is temporarily radially expanded such that the outer diameter of the gas seal is increased. The correction jig is used for correcting the outer diameter of the gas seal. The procedure in the aforementioned publication includes the following steps.    Step A: A cylindrical correction jig is attached to a portion of the injector closer to the injector body than the installation groove of the injector.    Step B: A combustion gas seal is fitted into the installation groove.    Step C: The correction jig is moved toward the nozzle distal end and relative to the injector. The outer circumferential surface of the gas seal is thus pressed by the inner circumferential surface of the correction jig. Accordingly, the correction jig corrects the increased outer diameter of the deformed gas seal.
However, with reference to FIG. 21, if the fitting step is performed from the side corresponding to the nozzle distal end, the gas seal 100 may be interfered with a slanted surface 102, which is formed in a portion of the installation groove of the injector with a diameter that gradually increases toward the injector body.
As has been described, the gas seal is radially expanded when fitted into the installation groove. Once reaching the installation groove, the gas seal starts to restore to the original shape, or the original diameter, by its elastic shape-restoring force. However, such restoration is hampered by the interference between the gas seal and the slanted surface, such that the gas seal is shaped in correspondence with the shape of the slanted surface. The shape of the gas seal thus may be varied among different products prior to the correction with the correction jig, and correction accuracy is lowered.
The same disadvantage is presented in the installation of the gas seal in an installation groove having a non-uniform diameter.
Further, in order to improve the sealing performance of the injector, the injector may include two gas seals installed in respective annular installation grooves, as described in Japanese Laid-Open Patent Publication No. 11-294302. The grooves are defined in the nozzle portion of the injector as spaced from each other at an appropriate interval. If the aforementioned procedure of the publication No. 2002-364494 is employed for installation of such gas seals, the steps A to C must be repeated, which complicates the procedure.